The project involves the study of the hydrogen isotope exchange kinetics of peptide NH protons in globular proteins, using bovine pancreatic trypsin inhibitor (BPTI) as a model globular protein. The object of hydrogen exchange studies in proteins is to elucidate the protein conformational dynamic processes that govern the exchange kinetics in native proteins. The kinetics of single, assigned NH's is measured from the decay of the 1H NMR signal in deuterium solvent. Five experiments are proposed. First, the kinetics of several protons for which exchange does not involve major unfolding will be characterized in BPTI. Second, the temperature and pH dependence of the exchange rates of single, assigned protons in Cys14-Cys38 reduced BPTI will be determined. The effect of 14-38 reduction on the total tritium exchange kinetics will also be determined. Third, isotope exchange rates of tryosine side chain OH's in BPTI and BPTI derivatives will be determined and compared to the rates of tyrosine ring flips, and the peptide NH exchange kinetics of atoms close to the tryosine side chains. Fourth, exchange rates of single protons at the BPTI-trypsin protein-protein interface will be prepared in an effort to determine whether a more stable form of this protein can be obtained. If this is possible, then the rates of exchange at high pH and high temperatures will be measured in an effort to determine a value, or a lower limit, for the frequency of the motions limiting hydrogen exchange kinetics in folded proteins.